I don't know what material it was, but a short TV insert showed a 3D printer "copying" a wrench. It was usable, so not a basic plastic.
While there's a lot of information around on the subject, I don't like to leave a question unanswered. So, it's both, and the thickness of the wick as well. Different thicknesses of resistance wire will have different resistance per inch, so the overall resistance is determined by the actual length of the wire. Best to use a multimeter to get precisely the resistance you want.
The first chart here had it the wrong way around. A thicker wire will have a smaller resistance, so it would need more length.
mrelwood, thanks for noticing! You are completely right on the last quote. Woody